1. Field of the Invention
This invention relates to a ceramic dielectric composition which has a high dielectric constant above 10,000 and which can be sintered at a temperature below 1,150.degree. C.
2. Description of the Prior Art
Up to this time, compositions, comprising BaTiO.sub.3 as a base raw material and additives such as CaTiO.sub.3, BaSnO.sub.3, CaZrO.sub.3, SrTiO.sub.3 and the like, have been used as dielectric materials for ceramic capacitors with a high dielectric constant. These materials have a relatively high dielectric constant to the extent of 2,000-25,000. However, these composition systems must be fired at high temperature to the extent of 1,300.degree.-1,400.degree. C. Therefore, while the cost of the firing becomes expensive, further problems have been encountered as follows.
Multilayer ceramic capacitors composed of these BaTiO.sub.3 systems should be fired at a high temperature above 1,300.degree. C. An internal electrode of these capacitors is fired with dielectric materials. Accordingly, noble metals having melting points higher than 1,300.degree. C., such as platinum or palladium, must be used for the electrode material as not to cause a reaction with the dielectrics or oxidation even at such high temperature. In another approach, compositions based by BaTiO.sub.3 are modified by the addition of some oxides having low melting points in order to lower the firing temperature below 1,150.degree. C. However, such compositions have dielectric constants of 3,000 at the highest. So far as such compositions are concerned, compositions which have dielectric constants above 10,000 have not been obtained.